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July 17, 2017 Broken Arrow, OK Tornado
Introduction The July 17, 2017 Broken Arrow Tornado was a large, violent multi-vortex tornado which wreaked havoc on several cities in Oklahoma before its dissipation. Due to heavy precipitation, extreme winds, several satellite tornadoes, and erratic movement, this tornado became the deadliest tornado in recorded history, as well as the largest. The tornado caused 1,856 fatalities, Meteorological Synopsis Supercell Formation On July 17, 2017, at 10:30 AM, the National Weather Service issued a Particularly Dangerous Situation Tornado Watch, due to extreme instability forming over the area as a low pressure system passed over northeastern Oklahoma. At 12:37 PM, a Severe Thunderstorm Warning was issued due to the rapid formation of a strong supercell around 55 miles southwest of Broken Arrow, which produced 55mph straight-line winds, hail to the size of softballs, and heavy rainfall. At 1:12 PM, a Severe Weather Statement was issued due to hail reaching the size of grapefruit, straight-line winds exceeding 90 MPH, and rainfall rates of 5 inches per hour, leading to numerous Flash Flood Warnings being issued. The supercell began tracking towards the city of Broken Arrow, and rotation began to develop. Tornado Formation At 1:30 PM, a Tornado Warning was issued due to strong low-level rotation about 20 miles southwest of Broken Arrow. 12 minutes later, a wall cloud was reported 4 miles southwest of the community of Bixby, slowly tracking to the southeast. 10 minutes later, debris was confirmed under the wall cloud. A small tornado formed, and began to turn to the left, until it faced northeast. Destruction of Bixby As the tornado began to track to the northeast, it picked up speed, and started to rapidly intensify. The wind speed accelerated from around 60 MPH to 140 MPH in only 5 minutes, and the tornado began to move towards a small community named Bixby. As the tornado approached Bixby, it continued to intensify, from wind speeds of 140 MPH to speeds 190 MPH, placing it near EF5 strength. Its movement speed also went from around 20 MPH to 90MPH in a matter of two minutes. The tornado directly hit Bixby, completely flattening the town and killing 300 people. Most fatalities were caused by citizens failing to head underground in time, due to the sudden directional change of the tornado, as well as the sudden movement speed increase of the tornado. The weather station had incorrectly reported that the tornado was headed southeast, and they had no way of knowing that the tornado was headed for Bixby, because their radar had malfunctioned and sent the same image multiple times, suggesting that the tornado had stagnated. The radar eventually sent the correct image, but the tornado was already very close to Bixby. This combination of factors left residents of Bixby only about 45 seconds to seek refuge from the tornado. 97% of all buildings in Bixby were completely destroyed, and 100% were rendered unusable. After destroying Bixby, the tornado continued to track northeast, and rain began to fall rapidly, obscuring the tornado. Several storm chasers to the northeast of the tornado were caught off-guard by the sudden rainfall, as well as the strengthening straight-line winds, which lead to several more deaths along the tornado's path towards Broken Arrow. Destruction of Broken Arrow Along its path towards Broken Arrow, Doppler Radar indicated that the tornado had expanded to 3.2 miles wide, and measurement tools indicated that winds had accelerated to 310 MPH. A Tornado Emergency was declared for Broken Arrow, as well as a PDS Tornado Warning for every county in Oklahoma northeast of the tornado due to its rapid movement speed and devastating winds. A satellite tornado was confirmed just before the tornado bore down on Broken Arrow. This satellite tornado would continue even after the dissipation of the Broken Arrow tornado, and would go on to become an EF3 tornado that derailed a train and mangled a gas pipeline, prompting several community evacuations. Thankfully, no fatalities and only 1 injury occurred with this tornado. However, the main EF5 tracked directly over the city of Broken Arrow at its peak strength, resulting in over 1,500 fatalities. The following notable damage was caused: * An custard shop was completely flattened. Part of the sign outside was found 2 miles away from Broken Arrow, embedded into the ground. * A slide was picked up from a water park and driven through the side of a brick building. * 3 hotels were completely destroyed. In every case, the concrete foundation was shifted and buckled. * A fire truck was mangled and thrown in a tree. * Intense ground scouring up to 11/2 feet in depth occurred across the entire path through Broken Arrow. * Several boxcars were found in various locations around town. One had been flung into a restaurant, and had buried itself in the restaurant's foundation. * A tall, poorly constructed building completely collapsed into the street, killing almost everyone inside. = Finale As the tornado left Broken Arrow, it weakened, but managed to produce a satellite tornado which reached EF4 strength. This tornado picked up a large car and hurled it into a storm shelter, resulting in serious damage and one death. This satellite tornado dissipated quickly afterwards. Weak, but refusing to dissipate, the main tornado slowly tracked over farmland, damaging a grain silo and a farmhouse, resulting in three injuries. Finally, after its half-hour destructive course, the tornado roped out and dissipated. Summary The tornado caused 1,856 deaths, 60,792 injuries, and billions of dollars of damage. The tornado broke many records, being the largest, most violent, and most deadly tornado ever recorded. 5 EAS alerts were issued during the event: two tornado warnings, and 3 Severe Weather Statements. The cities of Bixby and Broken Arrow were abandoned due to near-total destruction, leaving them nothing more than ghost towns. Extensive flash flooding occurred, resulting in widespread damage to many buildings. The supercell weakened below severe limits and disappeared 9 hours after the tornado started. Category:Tornadoes Category:Outbreaks